DC power network – review and analysis by the MBE KTN Philbert Chan (BRE) 1 November 2012

Outline of presentation About the MBE KTN Purpose of the work What we have done Report on findings Regulations and legislations Academic research Market and technology review Cost benefit analysis Potential application

About the Modern Built Environment KTN Funded by the Technology Strategy Board Delivered by ARUP, BRE, BSRIA and CIRIA Over 13,000 members from across the supply-chain Our Mission To increase the exploitation of innovation in the built environment for demonstrated business benefit.

About the Modern Built Environment KTN Currently focussing on four key themes: Climate Change Adaptation Energy & Carbon Efficiency Life Extension and Retrofit Process and Operational Efficiency URL: eb/modernbuiltktn eb/modernbuiltktn

Purpose To carry out a review and analyse the current state of DC power network To identify gaps in the knowledge and technology Legislations; Academic research; Current market and technology; Potential applications. Is DC power network a cost effective approach?  Provide information for developing a TSB funding competition specification

Workshops held Two workshops jointly held by the KTNs in London. Advantages of DC power networkDisadvantages of DC power network Efficiency (avoid inefficient conversion) Savings (reduce floor and ceiling void, potentially cheaper consumer goods) Security (Resilience from power outage, smooth load by storage, less interference) Devices (possibly less power and thermal management, ideal for batteries as power storage) Health and Safety (avoid unsafe 240VAC in schools, possibly lower electromagnetic emissions) Market opportunities (new market drivers, innovations) Cost (thicker cables for low-voltage system, expensive) Storage devices (inherently dangerous, lifetime) Technology (Difficulty in serving high power load, no zero crossings, need for DC/DC conversion) Safety (Arching problems, accidental cross connection with AC mains) Standards (no current stand, proprietary technologies are not interoperable) Changes (industry not ready for change, consumer benefit?)

Reports prepared Three separate reports prepared for the Smart DC SIG. First report: The background of why we should consider DC power; The basic requirements (controls and storage); Scope of the impact and the implications; A review of the current legislations, regulations and standards; A quick review on the current research activities on DC local power generation, and some existing commercial systems. Second report: Extended review on current research activities as well as existing commercial systems. Third report: Further focused review and cost benefit analysis

Report on findings – regulations and legislations No legislation or incentive to encourage micro-grid arrangements in the UK Supplier Licenses – a potential blocker Impact of cutting the tariff for PV panels within the FIT scheme – push other technologies forward? UK to set up a safe product registry for DC products, like the USA’s EMerge Alliance?

Report on findings – academic research A quick summary on the current academic research activities on DC power system (e.g. generation, storage, devices), including: DC distribution system; Micro-CHP; District generation; Power conversion; Fuel cells; Energy storage; Solid state lighting; Co-generation; Stirling engine; PV.

Report on findings – market and technological review Technologies for DC power distribution exist Currently used in small number of data centres Domestic use still at proof of concept stage Li-ion is currently the more promising energy storage technology and is in trial at present. However cost is likely to be high. Efficiency of power conversion, especially at partial load, still needs to be improved. Fuel cells technology is in pre-commercial trial in the UK, high potential. PV is the most mature and established renewable energy technology, but cost is still considered to be too high.

Report on findings – cost benefit analysis CBA is currently a major gap in the knowledge of DC power network. No credible CBA, especially for domestic building, was found within the project time frame. Many unknowns in defining a DC power network for analysis, e.g.: Bus voltage Cable size Topology of network Type of storage (if required) On or off grid Efficiency of various converters Costs (including installation, maintenance and appliances) are uncertain  Significant uncertainties in results

Report on findings – cost benefit analysis There is no clear cut case for either AC or DC technology at present. To facilitate a credible and robust CBA for DC power network: 1.To agree a set of DC & AC network applications, for both domestic and non-domestic use; 2.To define boundaries for each application; 3.To carry out an economic cost benefit analysis for each application as far as possible.

Potential applications Commercial Data centres Power over Ethernet (PoE) could be a potential technology Technologies in data centre could filter down to other commercial and domestic buildings Domestic Suitability to be determined; cost effective? New build? Retrofit? Community scale DC power network Demonstration of benefits to consumers, i.e. cost savings

Philbert Chan BRE Bucknalls Lane, Garston, WD25 9XX +44 (0)